MobilePros1 via eBay offers the open-box Mophie Juice Pack 6,000mAh Powerstation Pro Rugged Portable Battery Pack
, model no. 2028_JPU-PWRSTION-PRO, for $15.99
with free shipping
. That's $34 under the lowest total price we could find for a factory-sealed unit. It features a rubber shell with a stainless steel outer band, USB and microUSB charging ports, and an IP-65 rating for protection against dirt, sand, water, and other liquids.